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Success Stories If you have successfully repaired or restored a piece of equipment, why not write up what you did and post details here. Particularly if it was interesting, unusual or challenging. PLEASE DO NOT POST REQUESTS FOR HELP HERE! |
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1st Jan 2016, 8:29 pm | #1 |
Octode
Join Date: May 2003
Location: Belper Derbyshire
Posts: 1,910
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Maplin Minilab completed !!
good evening,
Over the Christmas holiday period I finally had time to make up and complete the Maplin Minilab project I was asking construction and circuit details of. It is a stabilised multi-voltage power supply built around 78XX and 79XX voltage regulators with 8 TTL inputs and outputs, a 1Hz/1KHz clock and a debounced switch. and ideal for testing and development of op-amp and digital logic circuits. This one I hope to teach my 2 sons when they start to grow up analogue and digital electronics. With a circuit diagram I bought all of the components needed to complete the project and I waited until I had every component before commencing with the project. I think I spent around £55 on components including £20 each for the transformer and case. I was extremely impressed with the quality of the case when it arrived. It is very well made and ideal for the task. It was a shame the 4mm test sockets I bought were of extremely dire quality and even the backnuts were not even round!! Some didn't even have a thread! I was surprised that anyone could have had the guts to sell them as sockets!! Belling-Lee or Mr. Bulgin would be spinning in their grave if they came out of one of their factories!!. You certainly have pot luck buying electronic components these days!! I managed to get some better ones and used these instead. The construction was fairly straightforward with no peculiar issues coming to light. The board construction took a few hours and the mechanical construction/wiring and testing took 2 days to complete. Other than the wiring of the mains switch was back to front which meant the neon was on all of the time, and the variable output pot worked in the wrong direction, the Minilab worked properly first time. I am very impressed with the outcome of the project and it should last a long time. Christopher Capener
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Interests in the collection and restoration of Tefifon players and 405 line television |
1st Jan 2016, 9:19 pm | #2 |
Dekatron
Join Date: Feb 2003
Location: Cottingham, East Yorkshire, UK.
Posts: 5,738
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Re: Maplin Minilab completed !!
Pleased to learn that you've completed the project and that it works Christopher. I've dropped a note to the member of the EPE 'Chatzone' who came up with the 'unobtanium' PCB, to let him know that it did get put to good use, having languished in his drawer for a couple of decades or more!
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David. BVWS Member. G-QRP Club member 1339. |
2nd Jan 2016, 11:00 am | #3 |
Dekatron
Join Date: Jul 2007
Location: Evesham, Worcestershire, UK.
Posts: 4,241
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Re: Maplin Minilab completed !!
Very good - nice and tidy
I used that exact case to build a bench PSU nearly 20 years back, and was also quite impressed with it. And not too expensive either. From what you say, it seems that they still available today - where did you buy yours from? All the best, Mark |
2nd Jan 2016, 11:48 am | #4 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 13,953
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Re: Maplin Minilab completed !!
Looks like a nice little project.
Those cases are really rather good: I've got a larger one here, containing a "roller-coaster" coil and 500pF wide-spaced variable capacitor for my 160/80/60/40M antenna tuner. |
2nd Jan 2016, 1:25 pm | #5 | |
Guest
Posts: n/a
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Re: Maplin Minilab completed !!
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2nd Jan 2016, 1:45 pm | #6 |
Dekatron
Join Date: Jul 2007
Location: Evesham, Worcestershire, UK.
Posts: 4,241
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Re: Maplin Minilab completed !!
But much more annoying if you've soldered the connections
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3rd Jan 2016, 11:57 am | #7 |
No Longer a Member
Join Date: Nov 2015
Location: Kilkenny, Ireland
Posts: 138
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Re: Maplin Minilab completed !!
You can get those cases from http://makerbase.co.uk/
I bought one to house a computer PSU to bench supply conversion. |
3rd Jan 2016, 12:08 pm | #8 |
Dekatron
Join Date: Jul 2007
Location: Evesham, Worcestershire, UK.
Posts: 4,241
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Re: Maplin Minilab completed !!
Thank you! Prices seem pretty reasonable too...
Mark |
3rd Jan 2016, 12:29 pm | #9 |
No Longer a Member
Join Date: Nov 2015
Location: Kilkenny, Ireland
Posts: 138
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Re: Maplin Minilab completed !!
They also trade on the bay as earthgazer if you collect Nectar points or other deals to make your purchase cheaper.
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3rd Jan 2016, 12:33 pm | #10 | |
Guest
Posts: n/a
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Re: Maplin Minilab completed !!
Quote:
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3rd Jan 2016, 1:43 pm | #11 |
Dekatron
Join Date: Jul 2007
Location: Evesham, Worcestershire, UK.
Posts: 4,241
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Re: Maplin Minilab completed !!
Not if you've done it properly (e.g. fed tinned wire through hole in terminal, wrapped around several times and "squeezed up" to get a good mechanical joint, applied heatshrink sleeving or equivalent to the completed joint, applied tie-wrap or similar mechanical support to the bundle of cables within an inch of the terminals, applied insulating boot over the whole assembly, applied tie-wrap to that to stop it coming away). In practice, it's easier to just give up and start again.
I suppose if you just "tack-solder" to the side of the terminals, then you might be right. But as we're talking about mains connections here, let's assume that we're not doing that... Besides, Christopher used push-on crimp connectors. Quite right, too |
4th Jan 2016, 10:47 am | #12 |
Heptode
Join Date: Jul 2008
Location: Selby, North Yorkshire, UK.
Posts: 979
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Re: Maplin Minilab completed !!
I'm going to have to get the one I built from the kit back in the late 1980s out and sort out the failed LM78xx components now. Mine's in the original plastic case that Maplin sold specifically for it.
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7th Jan 2016, 5:59 pm | #13 |
Hexode
Join Date: Mar 2005
Location: London, UK.
Posts: 318
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Re: Maplin Minilab completed !!
This thread reminded me that I too had built one of these from a Maplin kit. I haven't used it for years but I've dragged it out of the cupboard. It is certainly a solidly designed bit of kit and mine has a steel case with dark grey hammered finish cover. The components supplied were all of good quality even if the red plastic terminals have faded somewhat with age.
Now to check it out and perhaps give it a new lease of life. Edward |
17th Feb 2016, 9:36 am | #14 |
Heptode
Join Date: Jul 2008
Location: Selby, North Yorkshire, UK.
Posts: 979
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Re: Maplin Minilab completed !!
Here's mine - actually apart from the -5V regulator only putting out -2.5V, and the variable output voltage dropping when under any sort of load, it's all still working fine. The circuit is on the original veroboard soldered by a 15 year old me, back in 1989.
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